Cavity resonator high-frequency electron discharge device



l 1953 A. M; GUREWITSCH 2,634,383

CAVITY RESONATOR HIGH-FREQUENCY ELECTRON DISCHARGE DEVICE Filed Oct. 51, 1950 Inventor: Anatole MGur'ewibsch,

His Attorney.

Patented Apr. 7, 1953 UNITED CAVITY RESONATOR HIGH-FREQUENCY ELECTRON DISCHARGE DEVICE Anatole M. Gurewitsch, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 31, 1950, Serial No. 193,218

8 Claims. 1

My invention relates to high frequency electron discharge devices and associated apparatus and, more particularly, to such electron discharge devices and apparatus capable of handling comparatively large amounts of high frequency electric energy.

One object of my invention is to provide an electron discharge device having a comparatively simple and economical construction and yet capable of fulfilling high power requirements in high frequency electromagnetic circuitry.

' Another object of my invention is to provide an lectron discharge device which may easily be adapted to fulfill a number of different functions in high frequency circuitry such as to function as an amplifier, oscillator or detector.

Another object of my invention is to provide a high frequency electron discharge device which has a self-contained easily accessible electromagnetic field region which may be employed to efiect symmetrically the electric characteristics of an external cavity resonator circuit associated with the device.

A further object of my invention is to provide a high frequency electron discharge device which may be constructed to have internal tuning means whereby th resonant frequency of external cavity resonators associated with the discharge device may be controlled with little appreciable distortion of the resonator fields.

A still further object of my invention is to provide a high frequency electron discharge device which produces a self-contained electromagnetic field region through which input high frequency energy may be delivered and output high frequency energy may be taken without the resonator field distortion attendant upon the conventional direct coupling to cavity resonators associated with the device.

A still further object of my invention is to provide an electron discharge device which produces a self-contained electromagnetic field which may be employed to provide a predetermined interaction between input and output high frequency circuits of the device for such purposes as regenerative or degenerative coupling when the device is connected as an amplifier, or to provide feedback suificient to sustain oscillations when the device is employed as an oscillator.

Yet another object of my invention is to provide a high power high frequency electron discharge device having an electrode structure which facilitates cooling of the electrodes of the device.

In general, my invention comprises a plurality:

of annular electrodes supported in spaced planar extending along the axis of revolution of the device.

region or the device and is preferably divided into two sections by a central transverse disk or 1 septum which is connected to the control electrode of the device. The dimensions or the two wave guide sections thus formed are such as to produce a rapid attenuation of any electromagnetlc energy coupled tnereinto from the varla' mom of the electron stream. In other words, the wave guide sections are dimensioned to operate below "cut-off at the frequency of operatlon of the device. By inserting suitable tuning elements into the attenuated electromagnetic held produced within these wave guide sections, a reactive component may be reflected into the device in order to eifect a corrl'esponding variation in the resonant frequency of cavity resonators associated with the device. ihls self-contamed electromagnetic field region may also be used to provide input and output coupling to the device. in addition, suitable coupling elements such as apertures or interconnecting loops may be provided through the (K separating the two Wave guide sections in order to obtain any desired regenerative or degenerative coupling between input and output circuits of the device.

it will be appreciated that since this internal field region is located along the axis of the device, the introduction of tuning or coupling elements tnereinto has a symmetric loading elfect upon cylindrical cavity resonators generated around the axis so that little appreciable distortlon or the resonator rleld results.

i'he novel features which I believe to be characteristic of my invention are set forth with particuiarity in the appended claims. My invention itself, however, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a cross-sectional view of an electron discharge device embodying my invention; Fig. 2 is a similar cross-sectional view of the discharge device of Fig. 1 associated with suitable cavity resonators and incorporating structures whereby the internal electromagnetic field region may be employed for tuning purposes; Fig. 3 is a cross-sectional view of a cen- This internal wave guide is coupled'for high frequency energy to the electron stream tral portion of the electric discharge device of Fig. 1 showing a structure whereby the internal electromagnetic field region may be used for coupling purposes and also illustrating further modifications of my invention whereby a predetermined. internal coupling between input and output circuits of the device may be achieved.

Referring to Fig. 1, I have shown an electron discharge device 9 embodying my invention comprising a plurality of annular electrodes including a thermionic cathode I0, a control electrode II, and an anode I2 located in spaced alignment and formed around a central axis of revolution indicated by a line I3. Cathode I may be heated by any appropriate means such as an internal heating coil ma. An annular electron emitting surface I4 of cathode I 8 and a corresponding annular electron receiving surface I5 of anode I2 are located in close planar alignment to provide a short electron path therebetween. Cathode I0 also has a cylindrical portion I6 axially extending from the inner edge of electron emitting surface It to define an axially extending tube constituting a cylindrical wave guide I'l. Similarly, anode II has a cylindrical portion I3 extending from the inner edge of the electron receiving surface -I5 to define an axially extending tube constituting a cylindrical wave guide BS9. Wave guides I l and I9 comprise an internal electromagnetic field region of device '9 which communicates with the electron stream passing from cathode Iil to anode I2.

Control electrode I I is supported in conductive relation with a conductive disk 23 which extends transversely across the center of the device and which serves to divide the device into substantially symmetric input and output circuit portions. Preferably, the control electrode II is formed by merely perforating the disk 28, the perforations being in the form of an annular band located in the path of the electron stream. The central portion of the disk 20 serves as a septum dividing the Wave guide sections IT and I9 defined by cathode cylinder I6 and anode cylinder I8 respectively. Disk 23 also preferably extends radially beyond the outer surfaces of the cathode I0 and anode I2 respectively and terminates in a conector ring 2| which may be used to make connection from the control electrode II to cavity resonators associated with electron discharge device 9.

A pair of concentric cylindrical insulating members 22 and 23 comprising material, such as glass, completely pervious to high frequency electromagnetic fields, are hermetically sealed between the conductive disk 20 and the annular anode I2 on opposite sides of the electron receiving surface of the anode I 2 and function both to enclose the electrodes hermetically and to support the control electrode'II in proper spaced relation to the anode I2.' Similarly, concentric insulating members 24 and 25 are sealed between the conductive disk 20 and the annular cathode ID on opposite sides of theelectron emitting surface It in order to complete the enclosure of the electrodes and to maintain the cathode I9 and the control electrode II in proper spaced alignment. Preferably, annular ridges or shoulders '26 and 21 are formed in cylinder portions I6 and I8 respectively in order to provide a con venient seat for insulating members 2 3 and 22.

Inorder to provide a convenient high frequency by-pass connection between cathode I9 and a cavity resonator structure associated with device .9, whereby different unidirectional potentials may be applied to the cathode and the resonator without interfering With the flow of high frequency currents therebetween, I preferably secure around the outer circumference of the oathode It a conductive washer 28 separated from cathode It by a thin film 29 of high dielectric material, such as mica. .A similar high frequency capacitor comprising a washer 30 and a dielectric film 3I is preferably formed around the outer circumference of anode I2 to enable a high frequency connection between anode I2 and an associated cavity resonator. Although the incorporation of these high frequency capacitors into the structure of the discharge device 9, as described above, is to be preferred, it is not essential that they be so incorporated. Alternatively, suitable [high frequency by-pass connections may be incorporated into the structure of cavity resonators associated with device 9 in manners well known to those skilled in the art.

Wave guide sections I l and I9 are properly-dimensioned to cause a rapid attenuation of electromagnetic fields induced therein at the frequency of operation of discharge device 9. Due to the annular configuration of the electrodes of the device, the lowest order electromagnetic wave patterns which may normally be established within cylindrical wave guide sections I1 and I9 are the transverse electric Tizlo, or transverse magnetic 'IMo, first order modes of propagation P 1 enuated, i. e., the cut-off wave length, for such cylindrical wave guides is the diameter of the guide. For the transverse magnetic mode of operation, this cut-off wave length may be approximately determined by the following relationship (TMo) \=1.31d e and for the transverse electric mode For air, ILL e 1 so'that a' very simple relation-- ship between the diameter of the guide and the v cut-oil Wave length exists. It is only necessary,

therefore, to construct the cylinder portions I6.

and I8 to have a diameter small enough that the wave length of the electromagnetic waves produced in device 9 at the desired frequency of operation is longer than the critical cut-off wave length determined by the above formulas for the wave guides defined by these cylinder portions I6 and I8. V

As a result, an electromagnetic field is produced in waveguide sections I! and I9 during operation which is rapidly attenuated as it attempts to propagate away from the dividng disk 20 toward the open ends of the wave guide sections I? and I9 respectively. The electromagnetic field strength is normally attenuated to a negligible amount within less than one diameter at the frequency of operation of the device, as measured along the axis of the guide. The axial length of wave guide sections I1 and I9 is preferably however, at least'one wave-lengthlong at the desired frequency of operation of device9; If

acsgssa.

5.. a more complete attenuation of the internal field regions I! and I9 is desired, the inner walls of cylinders I6 and It may be tapered to a reduced diameter at the ends, or may be completely closed at the ends if the cylinders are of sufficient length to reduce the field intensit to a small enough value to preclude reflection of energy from the end walls.

The electron discharge device of Fig. 1 constitutes a completely operative component of a high frequency circuit. Although in the modifications of Figs. 2 and 3 to be described hereinafter, the internal electromagnetic field region produced during operation of the device is utilized for tuning or energy coupling purposes, the device 9 may be employed in the simple form illustrated in Fig. 1 without such inserted tuning or coupling elements. In fact, for exceptionally high power applications, it is preferable that device 9 be operated without such inserted elements because of the somewhat better cooling of the anode I 2 and control electrode II which results due to the better heat radiation from cylinder I8 and central disk 20. An even high rate of cooling can be achieved, if desired, by pass-' ing a cooling fluid within the wave guide sections I1 and I9. Tuning and coupling to device 9 can then be made within associated cavity resonators in a conventional manner.

Referring to Fig. 2, I have shown the electric discharge device of Fig. l in conjumtion with a pair of cylindrcal cavity resonators 32 and 33 respectively, resonator 32 constituting a gridcathode resonator for device 9 and resonator 33 constituting a grid-anode resonator. Resonators 32 and 33 may be constructed, as indicated, in an integral unit hav.ng a common wall 34 to provide three adjacent end surfaces terminating in suitable contact fingers 35 enabling a plug-in type connection with the discharge device 9 of Fig. 1. The major dimension of resonators 32 and 33 may be along the axis of the device 9, as shown, or may be the radial dimension, depending upon the desired direction of the electric vectors in the generated electromagnetic field of the resonators.

In the electron discharge device of Fig. 2, the wave guide sections I! and IQ are employed as regions in which tuning of the external cavity resonators 32 and 33 is accomplished. Within wave guide section II, I have shown one tuning arrangement and within region I9 I have shown an alternative tuning arrangement. It w.ll be appreciated that either of these tuning arrangements may be used in either or both regions II and I9.

The tuning arrangement shown in region II comprises a conductive rod 36 extending along axis I3 and telescoped within a conductive sleeve 36a which is supported by a Washer 37 composed of material, such as glass or polystyrene, which is pervious to high frequency electromagnetic fields. A non-conductive rod 38 composed of a field pervious material similar to Washer SI is attached to the end of conduct.ve rod 33 to enable adjustment of the axial depth of conductive rod 38 Within region I'I.

As will be apparent to those skilled in the art, due to the presence of the axially extending conductive rod 36 and sleeve 35a, the portion of electromagnetic field region 51 coextensive with rod 36 and sleeve 36a, designated as portion I'Ia, now constitutes a concentric transmission l;ne; while the portion of region II lying between the end of sleeve 36a and the open end of cylinder I6, designated as portion I'Ib, constitutes a wave guide beyond cut-off. Region IIb preferably has an axial length equal to at least one inner diameter of cylinder I6 to provide substantially complete attenuation of electromagnetic energy coupled into line I'Ia. Consequently, portion I'Ia of region II appears to the dischargedevice 9 as an open ended concentric transmission line terminating in almost infinite impedance. By adjusting the combined length of rod 36 and 36a, this concentric line can be made to reflect any desired reactive component either capacitive or inductive into the field produced by the electron stream of device 9. Moreover, the axial depth of rod 36 with relation to conductive disk 20 may be adjusted to control the degree of coupling produced by the internal attenuated field region adjacent the electron stream between the resonant circuit represented by the concentric line Ila and the resonant circuit represented bycavity resonator 32.

The tuning arrangement shown within region I9 operates upon substantially the same princi-" ple as that shown in connection with region I! I with the exception that the concentric line section terminates in a tuning plunger to produce a closed ended line of variable length. A conductive rod 35 ax-ally inserted within region I9 is short circuited along its length for high frequency energy by an annular tuning plunger 40 to define a closed ended concentric line Isa. By adjusting the position or plunger 40 relative to rod 39 the line Isa can be made to renect any desired reactive component into the internal attenuated neld region produced by the electron stream, and consequently to vary the frequency of resonance of grid-anode resonator 33 accord- 4 I are located along the axis of device 9, the gen'- erated radial fields produced by device 9 are affected symmetrically, and consequently there is little appreciable distortion of the resonator field patterns due to the presence of these central tuning elements.

In the modifications of my invention illustrated in Fig. 2, input and output coupling of the high frequency energy to the resonant circuits, may be accomplished by any suitable means, such as coupling loops II associated with cavity resonators 32 and 33. Proper potentials for operating the high frequency apparatus of Fig. 2 as an amplifier, oscillator or detector, may be supplied to the various electrodes of discharge device 9.

through suitable connecting terminals such terminals 50.

Referring now to Fig. 3, I have shown a further modification of my invention wherein the central Wave guide sections II and I9 are employed for coupling high frequency energy to the input circuit of the device and for extracting high frequency energy from the output circuit of the device. In this modification, high frequency electrio coupling elements and 43, terminating in Moreover, since the tuning elements of my invention, such as rod 36 and sleeve 36a, or rod 40 and plunger 7 coupling disks and 'fed'by coaxial cable terminal connectors 44, are inserted along the axis of the device within the wave guide sections I1 and it somewhat in the same manner as the tuning elements of Fig. -2. Other well known types of high frequency coupling elements, such as probes, dipoles, or loops may alternatively be used. The electromagnetic field established within wave guide H by the input coupling element e2 produces :a cor-responding variation in the electron stream of discharge device 9 so that high irequ'ency fields are'set up within grid-cathode and grid-anodecavity resonators, such as resonators 32 and 33 of Fig. 2,-associated with device 9. As the "coupling elements 32 and-i3 are moved closer to the central septum 2 0, -'a tighter coupling is achieved to the electron stream and ultimately to the high frequency energy within the resonators 32 and 33. Here again, as with the tuning elements, it will be appreciated that the coupling is symmetric with relation to the resonator fields with the result that there is little appreciable field distortion and a consequent greater efficiency.

Inthemodifications 'o'i Fig. 3, I'have also shown the central septum 26 as including an energy transferring element, such as an aperture '45 through which an intercoupling member til is passed, to provide coupling between the wave guide sections "ii and I9. By means of such apertures, with or without additional intercou pling members, any desired degree and phase of direct coupling between input and output circuits,' can be achieved. The design and effect of such'energy transferring elements between input 7 and output cavity resonators of high frequency devices is 'well known to those skilled in the art. However, the location of the energy transferring elements between internal auxiliary field regions of an associated electron discharge device, as in the present invention, has the very markedadvantage of causing little or no deformation of the field pattern in'the resonators.

It will thus be seen that I'have provided a high power,'.high frequency electron discharge device which has a self contained auxiliary electromagnetic field region which can'be used to aliect symmetrically the electron flow in the discharge device and in the electromagnetic fields produced in cavity resonators associated with the device. The annular electrodes themselves provide. a greater'current handling capacity for the discharge device than is normally available from the smaller circular electrodes usually found in such high "frequency devices. In addition, the central disk which is conductively connected to control electrode H facilitates cooling of the control electrode H; and the central cylinder '82,

which defines the wave guide section H, has the large surface area desirable for radiation cooling of the annular anode '52 of device 9.

It is to be understood that although I have shown particular embodiments of my invention, many other modifications can be made, and I intend, therefore, by the appended claims to cover all such modifications as i all within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high frequency electron discharge device comprising a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to said control electrode and extending across the central region defined by said .annular electrodes substantially in the plane of said control electrode, a pair of conductive cylinders extending axially from .said cathode and said anode respectively to define a pair of electromagnetic field regions axially separated by said disk which field regions communicate with an electron discharge from said cathode to said anode, said cylinders each having a wave propagation cut-oil characteristic to electromagnetic waves having frequencies "equal to the operational frequencies of said device, and a tuning element inserted along the axis of at least one of said field regions for introducing a reactive component into the field of an electron discharge of said device.

'2. A high frequency electron discharge device comprising a plurality of annular electrodes in cluding a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to'said control electrode and extending across the central region defined by said annular electrodes substantially in the plane of said control electrode, a pair of conductive cylinders extending axially from said cathode and said anode respectively to define a pair of electron discharge communicating electromagnetic field regions axially separated by said disk, said cylinders each having a wave propa gation cut-off characteristic to high-frequency electromagnetic waves, and a .high frequency electromagnetic energy coupling element inserted along the axis of at least one of said electromagnetic field regions to provide electromagnetic energy coupling to an electron discharge from said cathode to said anode.

v3. A high frequency electron discharge device comprising a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes substantially in the plane of said control electrode, a pair of conductive cylinders extendingaxially from said cathode and said anode respectively to define a pair of electron discharge interacting electromagnetic field regions axially separated by said disk, said cylinders having diameters less than the wave propagation cut-oil?- diameter for electromagnetic waves having a frequency equal to a frequency of operation of the device, and said disk having an energy transferring element passing therethrough for providing couplingof electromagnetic waves from one of said electromagnetic field regions to the other.

4. High frequency apparatus comprising anelectron discharge device having a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment and all having acommon axis of revolution, a conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes in a plane perpendicular to said axis of revolution, a pair of conductive cylinders extending axially from said cathode and said anode respectively to define together with said diska pair of axially separated electromagnetic field regions interacting with an electron discharge from said cathode to said anode, a pair of cavity resonators extending around the periphery of said discharge device and connected to said electrodes to form a grid-cathode resonator and a grid-anode resonator respectively,

and a tuning element inserted along the axis of at least one of said field regions for introducing a reactive component into said electron discharge, thereby to tune a corresponding one of said resonators.

5. High frequency apparatus comprising an electron discharge device having a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a, conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes, a conductive cylinder extending axial- 1y from said cathode to define together with said disk an electron discharge interacting electromagnetic field region, a grid-cathode cavity resonator extending around the periphery of said discharge device, and a tuning element inserted along the axis of said electromagnetic field region for reflecting a reactive component into said electron discharge, thereby to tune said resonator.

6. High frequency apparatus comprising an electron discharge device having a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes, a conductive cylinder extending axially from said anode to define together with said disk an electron discharge interacting electromagnetic field region, a grid-anode resonator extending around the periphery of said discharge device, and a tuning element inserted along the axis of said electromagnetic field region for reflecting a reactive component into said electron discharge, thereby to tune said resonator.

7. High frequency apparatus comprising an electron discharge device having a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes, a conductive cylinder extending axially from said cathode to define together with said disk an electron discharge interacting cylindrical Wave guide, said wave guide having a propagation cut-off characteristic to high frequency electromagnetic waves in the apparatus, a grid-cathode cavity resonator extending around the periphery of said discharge device, and a high frequency coupling element inserted along the axis of said wave guide to efiect a transfer of high frequency electromagnetic energy with said resonator.

8. High frequency apparatus comprising an electron discharge device having a plurality of annular electrodes including a cathode, a control electrode and an anode located in consecutive spaced planar alignment, a conductive disk connected to said control electrode and extending across the central region defined by said annular electrodes, a conductive cylinder extending axially from said anode to define together with said disk an electron discharge interacting electromagnetic field region, said cylinder having a diameter less than a wave propagation supporting diameter for high frequency electromagnetic Waves in the apparatus, a grid-anode resonator extending around the periphery of said discharge device, and a high frequency coupling element inserted along the axis of said field region to effect a transfer of high frequency electromagnetic energy with said resonator.

ANATOLE M. GUREWITSCI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,407,274 Hartley Sept. 10, 1946 2,409,693 Okress Oct. 22, 1946 2,427,693 Ryder Sept. 23, 1947 2,434,115 McArthur Jan. 6, 1948 

